Strong Fist (剛拳, Gōken) is Guy's and Lee's characteristic fighting style, the purpose of which is to cause external damage and break bones. It is the exact opposite of Gentle Fist which is used mainly by the Hyūga clan.[1] This style of fighting involves smashing your opponent and is generally used only by extremely physically powerful and dominating shinobi.

Trivia

Sasuke and Kakashi do not actually practise this style, but they use the key elements and a few techniques that were copied with their Sharingan from Rock Lee and Might Guy.